Position detecting apparatus of capsule endoscope, capsule endoscope system and computer readable recording medium

Abstract

A position detecting apparatus of a capsule endoscope includes a receiving antenna unit that receives a wireless signal transmitted together with an image data signal from the capsule endoscope in a subject via a plurality of receiving antennas, a correlation level calculating unit that calculates a correlation level between the image received by the receiving antennas and an image received immediately before the image was received, a determining unit that determines whether a position and/or direction of the capsule endoscope is changed, based on the correlation level calculated by the correlation level calculating unit, and an estimating unit that estimates the position and/or direction with respect to the position of the capsule endoscope at the time the image was captured if the determining unit determines that the position and/or direction of the capsule endoscope is changed.

What is claimed is: 
     
         1 . A position detecting apparatus of a capsule endoscope, comprising:
 a receiving antenna unit that receives a wireless signal transmitted together with an image data signal from the capsule endoscope in a subject via a plurality of receiving antennas;   a first storage unit that stores a first image received by the receiving antennas;   a second storage unit that stores a second image received subsequently to the first image;   a correlation level calculating unit that calculates a correlation level between the first image stored in the first storage unit and the second image stored in the second storage unit;   a determining unit that determines whether a position and/or a direction of the capsule endoscope is changed, based on comparison of the correlation level between the first and second images calculated by the correlation level calculating unit with a specified threshold value;   an estimating unit that estimates the position and/or direction of the capsule endoscope at the time the second image was captured by an imaging unit of the capsule endoscope if the determining unit determines that the correlation level is smaller than the specified threshold value; and   a third storage unit that stores the second image stored in the second storage unit in association with information of the position and/or direction estimated by the estimating unit.   
     
     
         2 . The position detecting apparatus of the capsule endoscope according to  claim 1 , wherein
 the correlation level calculating unit calculates a normalized cross-correlation value or a residual sum of squares as the correlation level.   
     
     
         3 . The position detecting apparatus of the capsule endoscope according to  claim 1 , wherein
 the correlation level calculating unit calculates a movement amount of a specified region in an image as the correlation level.   
     
     
         4 . The position detecting apparatus of the capsule endoscope according to  claim 3 , wherein
 the correlation level calculating unit calculates the movement amount through image processing using a block matching method or an optical flow.   
     
     
         5 . The position detecting apparatus of the capsule endoscope according to  claim 1 , further comprising a fourth storage unit that stores theoretical electric field strengths of the wireless signal received by each of the receiving antennas, according to the position and direction of the capsule endoscope in the subject, wherein
 the estimating unit includes:   an electric field strength comparing unit that acquires the theoretical electric field strengths from the fourth storage unit and compares specified values that are calculated from a difference between received electric field strengths of the wireless signal received by each of the receiving antennas and the theoretical electric field strengths; and   a position determining unit that determines the position or the position and direction of the capsule endoscope in which the image data was captured, based on results of the comparison by the electric field strength comparing unit.   
     
     
         6 . The position detecting apparatus of the capsule endoscope according to  claim 1 , wherein
 the receiving antenna unit has a sheet shape on which the plurality of receiving antennas are arranged.   
     
     
         7 . The position detecting apparatus of the capsule endoscope according to  claim 5 , further comprising a trajectory calculating unit that calculates a trajectory of the capsule endoscope from the position of the capsule endoscope determined by the position determining unit. 
     
     
         8 . A capsule endoscope system comprising:
 a capsule endoscope that acquires image data of a subject;   the position detecting apparatus according to  claim 1  that receives the image data transmitted from the capsule endoscope and estimates the position and direction of the capsule endoscope when the position and/or direction of the capsule endoscope is determined to be changed; and   an image display unit that acquires the image data and position information of the image data from the position detecting apparatus and displays the acquired image data and position information.   
     
     
         9 . The capsule endoscope system according to  claim 8 , wherein
 the image display unit displays the image data and displays a moving trajectory of the capsule endoscope in the subject calculated by the trajectory calculating unit.   
     
     
         10 . A non-transitory computer readable recording medium storing an executable position determination program, the position determination program causes a processor of a position detecting apparatus that receives image data transmitted from a capsule endoscope in a subject and estimates a position and a direction of the capsule endoscope in which the received image data was captured, to execute:
 acquiring a wireless signal which is transmitted from the capsule endoscope and received by a plurality of receiving antennas of a receiving antenna unit;   extracting an image from the wireless signal received by the receiving antennas;   calculating a correlation level between the extracted image and an image received immediately before the extracted image was received;   determining whether the position and/or direction of the capsule endoscope is changed, based on the calculated correlation level by the correlation level calculating procedure; and   estimating the position and/or direction of the capsule endoscope in which the image was captured if the position and/or direction of the capsule endoscope is determined to be changed by the determining procedure.